Analytical instruments which rely upon regulated fluid flow are commonly employed in a wide variety of applications, such as sample purification, chemical analysis, clinical assay, and industrial processing. Such instruments typically function through devices which operate by initiating, maintaining, halting, or reversing a flow stream through the device. This may be accomplished by combinations of valves and/or pumps. Very often, such instruments devices require multiple flow paths to operate efficiently. Generally, efficient operation requires a flow system combining flow-through components, such as sorbent columns and connective tubing, with terminal components, such as needles, pumps, and drains. Different flow paths are frequently required to, for example, isolate a component from the flow system, include a component into the flow system, or rearrange the order of the components in the flow system. For many systems, an extensive and complex array of tubing, fittings, and the like are employed to provide the many flow paths that are necessary for optimum operation.
Combinations of commercially-available valves are often necessary to provide a number of flow paths among the flow-through components and terminal components employed in a flow system. Further, there is the need to sense certain characteristics of the fluid flow at differing points in the flow paths. Examples of such sensed characteristics include the pressure, flow rate, and temperature of the fluid. Other characteristics related to the particular fluid flow include the presence or absence of a fluid component, such as an analyte or contaminant. Such needs are typically addressed by the attachment of differing, plural sensors. There exists the practical problem, therefore, of connecting the large number of valves, sensors, fittings, and the like that are required for the multitude of flow path combinations in a modern analytical instrument.
Further, such flow systems involve a large number of flow-through and terminal fluid connections which increases the complexity, expense, and physical volume of the flow system. Such fluid connections are difficult to implement, especially when minimum volumes within the flow system are desirable. The complexity of such systems also introduces reliability concerns. Because the devices that are implemented in these flow systems are sometimes automated, the reliability and accessibility of the flow system are features critical to successful instrument operation.
Another problem involves the function of properly orienting all of the valves, sensors, and the like so as to allow the desired combinations of flow paths, yet also provide a flow system that is compact, easily-manufactured, inexpensive, and reliable. For example, the provision of fluid-tight connections in a complex fluid-handling assembly has become exceedingly problematic as the assembly is reduced in size. Some instruments, such as a gas chromatograph, employ fluids in the form of combustible gasses in performing an analysis. Even though the pneumatic fittings in the typical chromatograph are designed to minimize leakage, one may nonetheless consider a pneumatic fault mode wherein a gas leak could occur and sufficient gas could accumulate so as to pose an unsafe condition.
It will also be appreciated that a flow system must be versatile, that is, capable of being reconfigured during an instance of repair or modification, or to meet the requirements of a particular application as additional valves, fittings, etc. are added to the flow system.